This application relates to electrical controls and, more particularly, to controls for regulating a plurality of separate loads. The invention is particularly applicable to controls for regulating a plurality of separate heating elements and will be described with specific reference thereto. However, it will be appreciated that the invention has broader aspects and can be used for regulating a plurality of electrical loads other than heating elements.
Electrical cooking ranges commonly have a plurality of separate heating elements that are individually controllable. One type of control is a bi-metal thermostat having an internal heater. The spring force on the bi-metal is manually adjustable to vary the temperature of the heating element and there is no temperature feedback from the heating element to the control.
Another type of control uses a high current relay for each heating element. The relays are opened and closed in accordance with the temperature measured by sensors located adjacent the heating elements. Relays that are capable of handling 10-15 amps for a 2,000 watt heating element are very expensive, particularly when they are required to provide an extended full load cycle life.
Another type of control uses a high current semi-conductor such as a triac for each heating element. The triacs allow control of power to each heating element and provide fairly accurate temperature control but it is expensive to use an individual triac and an associated heat sink for each heating element.
It would be desirable to provide a control arrangement that eliminates disadvantages of prior systems while still providing variable control of each heating element.